A broad class of continuous chip fryers, for example, potato chip and french fry fryers, which require more heat than can be directly applied at the fryer, uses external heat exchangers to heat the oil. The heated oil transfers heat to the chips in the fryer and then returns to the exchanger. The chips in the fryer either float up against a hold down mesh belt known as a submerger or are supported by a conveyor. In either case, the chips form a bed. Since the frying time needed is determined by the product, the production capacity, or rate, of a given size fryer is determined by the depth, or thickness, of the bed. If, for a given size fryer, the production rate and the associated bed thickness are increased, a limit is reached beyond which the frying becomes non-uniform. This limit is the maximum production capacity of this fryer size.
It was discovered that the reason for the non-uniform frying is the shielding of the center layer chips by the outer, top and bottom layer chips from the flow of heated oil from the exchanger. This shielding increases with the bed thickness.
It was also discovered that this shielding effect can be overcome by changing the oil flow pattern.